The present invention is useful in optical systems, and in particular, in optical systems that create a perceivable image of an object by the transmission of radiation through a lens. The present invention has particular application to light microscopes that use an iris diaphragm to enhance certain characteristics of the image created in the microscope. The broad concepts of the invention are particularly useful in cameras, as well
A standard element of almost all modern light microscopes is a variable diameter (diaphragm) iris disposed at the aperture of the objective lens or at a plane conjugate to the objective aperture to control the area of the lens that passes light. To clearly distinguish over the prior art, the term xe2x80x9caperture maskxe2x80x9d is used instead of xe2x80x9ciris diaphragmxe2x80x9d when referring to the mechanism that shapes a beam of light incident on a lens. As used herein, the term xe2x80x9cobjective aperturexe2x80x9d shall mean, and will be understood by those skilled in the art to be, a lens aperture (or back focal plane) or any aperture conjugate to a lens aperture.
The prior art teaches that by effectively decreasing the area (diameter) of the lens that passes light by closing down the iris diaphragm, the contrast and depth of field of the perceived image is increased, while light intensity and resolution are decreased. Iris diaphragms used for the foregoing purpose have not changed materially for many decades. Investigators using a microscope with such an iris are able to adjust the iris to obtain the best combination of contrast, depth of field and resolution for the particular investigation being conducted.
The degradation of resolution by increasing contrast and depth of field with an iris diaphragm is a result of the iris blocking light from the outer portions of the lens, thereby reducing the working numerical aperture (NA) of the lens and hence reducing the higher order image-forming diffraction wavelets that pass through the lens. This phenomenon is explained in detail in Dr. Greenberg""s U.S. Pat. No. 5,345,333.
The present invention provides a manually controlled dynamic aperture mask for an image-forming lens that: (a) increases image contrast and depth of field without compromising image resolution; (b) generates motion parallax to create a 3D image; (c) creates hand-eye-brain feedback (through motion parallax) that unambiguously resolves foreground from background, thus producing a more accurate 3D image; (d) permits 2D viewing from any selected angle and view position; and (e) allows 2D and stereo pair photographs to be taken from any angle and position (not just along a single axis).
A manual control module, such as a joystick, mouse, keyboard or the like, controls the size and position of a sector-shaped mask aperture. The size of the sector-shaped aperture in the mask determines the angle of view, while the angular position of the aperture sets the position of view. When the mask is effectively removed from the path of the image-carrying light beam, the object is viewed from directly above (along a normal to the object), as is typical in prior art imaging devices. When a mask with a sector-shaped aperture is disposed in the path of the beam, the angle of view is oblique to the optical axis in an amount dependent on the size of the sector-shaped aperture. As the size of the aperture decreases, the angle oblique to the normal increases. Rotation of the mask and sector-shaped aperture changes the direction from which the object is viewed at the angle of view determined by the size of the aperture. Manipulation of the joystick to sweep a selected sector mask aperture through an arc creates motion parallax, which creates a viewable 3D image without the need for special 3D display equipment.
The manual control of the dynamic aperture mask permits the hand-eye-brain connection to resolve any ambiguities between foreground and background in a 3D image produced as described above.
The variability of the size of the aperture mask permits the investigator to finely tune the system to create the best match between the object under investigation and the optical system imaging that object.
The terms xe2x80x9csectorxe2x80x9d or xe2x80x9csector of a circlexe2x80x9d are used herein to mean that portion of a circle which includes an arc of the circle and the center of the circle. The terms xe2x80x9caperturexe2x80x9d or xe2x80x9copeningxe2x80x9d as used herein mean light transmissive, as opposed to opaque, and do not necessarily mean without physical structure.
Because of the particular geometry of a sector of a circle, a single mask having a variable-size, sector-shaped aperture can be used with lenses of different numerical apertures and magnifications.
Another advantage of the present invention is that the light beam which passes through the sector-shaped aperture of the mask is oblique with reference to the optical axis of the lens, thus having functional capabilities well beyond those of a co-axial beam emanating from a standard prior art circular, co-axial, variable-diaphragm iris.
By positioning the sector-shaped aperture of the mask of the present invention at different locations about the optical axis of the objective lens, the object is viewed from different directions or oblique angles relative to the optical axis. The degree of obliquity is further controlled by the angular opening of the sector-shaped aperture. For example, a 90-degree mask aperture will produce a greater angle of obliquity than a 180-degree mask aperture.
When a particular direction of view reveals details of interest, stereo pair photographs can be taken of that view; one from the selected angle and one from an anglexc2x1180 degrees thereto.
Accordingly, it is an object of the present invention to provide a manually controlled dynamic, sector-shaped aperture mask for selecting angled views of an object from different points of view and creating 3D images of the object.
It is a further object of the present invention to provide a manually controlled dynamic, sector-shaped aperture mask which permits stereo pair photographs of an object to be taken from different angles of view.
Another object of the invention is to provide an improved and universal mask that functions equally with lenses of different numerical apertures and magnifications.
It is a further object of this invention to provide the user with hand-eye-brain feedback in order to produce a more accurate 3D image of the object.
It is still another object of the invention to create 3D images by motion parallax so that a 3D image can be perceived without the need for special 3D display equipment. The advantage is that an observer can perceive a 3D image, even if the observer is viewing the object with only one eye. Thus, the motion parallax 3D image can be recorded and presented on standard video equipment.
Other advantages and objects of the invention will be apparent to those skilled in the art from the description of the invention which follows with reference to the following drawings.